Cyclic process for desulfurizing crude petroleum fractions with sodium

ABSTRACT

AN INTEGRATED PROCESS FOR THE DESULFURIZATION OF CRUDE OIL OR SIMILAR VIRGIN HYDROCARBON FRACTIONS WHEREIN A DISPERSION OF METALLIC SODIUM IS EMPLOYED TO REACT WITH THE SULFUR CONTAMINANTS PRESENT WITHIN SUCH CRUDE OIL TO FORM A SODIUM SULFIDE PRECIPITATE ELIMINATED FROM THE TREATED CRUDE THROUGH CENTRIFUGATION. THE INTEGRATED SYSTEM IS PROVIDED BY REACTING THE SODIUM SULFIDE PREDIPITATE WITH HYDROCHLORIC ACID TO PRODUCE SODIUM CHLORIDE WHICH AFTER RECLAMATION CAN BE EMPLOYED THROUGH ELECTROLYSIS TO PROVIDE THE NECESSARY SODIUM FOR DESULFURIZATION OF THE CRUDE OIL.

United States Patent 3,565,792 CYCLIC PROCESS FOR DESULFURIZING CRUDEPETROLEUM FRACTIONS WITH SODIUM Frank B. Haskett, Ocean City, N.J.,assignor of ten percent to Joan Hixon Martin, Washington, D.C. FiledJune 7, 1968, Ser. No. 735,397 Int. Cl. Cg 19/08, 29/04, 31/14 U.S. Cl.208208 3 Claims ABSTRACT OF THE DISCLOSURE The present invention relatesto a process for the desulfurization of crude oils or similar virginhydrocarbon fractions and, more particularly, to an integrated processof desulfurizing such crude oils wherein metallic sodium is employed.

Due to the ever-increasing concern about air pollution, a great deal ofstudy has been conducted in recent years to develop efficient andeconomical means of reducing the sulfur content present in crudepetroleum oils and other virgin hydrocarbon fractions. In this respect,tolerances are now being set which limit the maximum sulfur contentpermissible in various types of refined petroleum products. Thus, forexample, heating oils, gasolines, etc., will be limited to stricttolerances in the maximum amount of sulfur content present therein so asto effect a reduction of the air pollution associated with the burningof such petroleum products having high sulfur contents.

While various and sundry process and techniques for reducing the sulfurcontent of hydrocarbon fractions have been developed in the past, mostof such processes have involved complicated and expensive catalyticreactions, which reactions cannot be economically, justifiably employedto reduce the sulfur content of the hydrocarbon material below thoselimits which are now being set. Accordingly, there has been a great dealof concern and investigation relative to the production of a simple andefficient method of reducing the sulfur content of hydrocarbonfractions, particularly crude oil and similar virgin hydrocarbonmaterials.

While the use of alkali metals in the refining of hydrocarbon oils hasbeen previously proposed, such use of alkali metals has been generallylimited to the treatment of refined petroleum fractions, the treatmentbeing c0nducted at elevated temperatures for the purpose of removing aninsoluble polymer from the refined hydrocarbon fraction. In thisrespect, US. Patent 1,952,616 is exemplary of those patents dealing withthe refining of hydrocarbon materials, e.g. fractionated lubricatingoils with a molten alkali metal at an elevated temperature so as toproduce and agglomerate a polymer byproduct and separate such insolublematerial from the refined oil. Similarly, where it has been proposed toemploy alkali metals for the desulfurization of hydrocarbon oils, suchdesulfurization has generally been conducted by heating a refinedpetroleum distillate or fraction with a molten alkali metal at asuitable temperature so as to cause the necessary reaction between thealkali metal, e.g. sodium, and sulfur content of the refined hydrocarbonfraction.

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The process of the present invention is clearly distinguished from anyof these prior art processes by providing a simple, efiicient unitaryprocess for the desulfurization of crude oils and other virgin petroleumfractions by the utilization of sodium metal. Thus, in accordance withthe present invention, the sulfur content and metallic content of crudepetroleum fractions are reduced below acceptable maximum limits byreacting the crude petroleum fraction with a dispersion of sodium metalat ambient temperatures, a solution of sodium chloride suitable forreplenishing the supply of sodium metal through electrolysis beingproduced by a reaction of the sodium sulfide dispersion, obtained byreacting the crude petroleum fraction with the dispersion of sodium,with hydrochloric acid. Accordingly, a unitary, cyclic process isprovided wherein the desulfurization of crude petroleum oils and othervirgin petroleum fractions is provided in a simple and efiicient manner.

Accordingly, it is a principal object of the process of the presentinvention to provide a method for the desulfurization of crude petroleumfractions, e.g. crude oil, in a manner which eliminates the inherentdisadvantages and deficiencies of prior art processes.

It is yet a further object of the process of the present invention toprovide such a process for the desulfurization of crude oil and othervirgin petroleum fractions wherein a dispersion of sodium metal isemployed to react with the crude oil at ambient temperature so as toremove sulfur and metal contaminants.

A further object of the present invention is to provide a simple andefiicient cyclic process for the desulfurization of crude petroleumfractions so as to reduce the sulfur content thereof below maximumacceptable limits, such desulfurization being conducted by reacting thecrude petroleum oil with a dispersion of sodium metal with subsequentreplenishing of the sodium metal employed.

A still further object of the process of the present invention comprisesa desulfurization of crude petroleum oils wherein the sodium sulfideprecipitate formed by the reaction of sodium metal with the crude oil isfurther reacted with hydrochloric acid so as to produce a solution ofsodium chloride useful in the production and replenishing of sodiummetal by electrolysis.

Still further objects and advantages of the novel process of the presentinvention will become more apparent from the following more detaileddescription thereof and the descritpion of the accompanying drawingswherein the figure is a diagrammatic representation of the process ofthe present invention.

As described previously, the process of the present invention isapplicable to the desulfurization of crude or virgin petroleum oils.Thus, in accordance with the process of the present invention, a coldcrude oil or other virgin hydrocarbon fraction is desulfurized and themetal contaminants removed therefrom by contacting such cold crude oilor other virgin hydrocarbon fraction with a dispersion of sodium metal.In this respect, the reaction between the sodium metal and the sulfurcontaminants present in the cold crude oil or other virgin hydrocarbonfraction can be simply represented as follows:

As can be seen from the above, the desulfurization of the cold crude oilor other virgin hydrocarbon fraction in accordance with the process ofthe present invention is accomplished by the formation of sodium sulfideformed as a precipitate by the reaction of sodium metal with the sulfurcontaminants. In addition, metal contaminants present in the cold crudeoil or other virgin hydrocarbon fraction will be displaced in a similarmanner by the sodium metal and, accordingly, will appear either as asulfide of the displaced metal or as a pure metal itself in precipitatedand agglomerated form. The basic metal contaminants found in crude oilinclude, for example, nickel, molybedenum, vanadium and cobalt. Sinceall of these metals are heavier than sodium, and more electro-negativethan sodium, they will be displaced by the addition of the sodiumdispersion to the cold crude oil or other virgin hydrocarbon fraction.

It can therefore be seen that the contacting of the crude oil with adispersion of sodium metal acts in a two-fold manner, i.e., to reducethe sulfur content of the crude oil or other virgin hydrocarbon fractionby the formation of a precipitate, i.e., sodium sulfide, and to removemetal contaminants generally present in the crude petroleum fraction bya displacement of the same with the sodium metal. Most important,however, is the reduction of the sulfur content by the utilization ofthe dispersion of sodium metal since, as noted previously, there hasbeen a great deal of concern recently relative to air pollution, etc.,relating to the high sulfur content of fuels and similar petroleumproducts utilized.

In addition to providing for desulfurization and demetallization of thecold crude oil or other virgin hydrocarbon fraction, the process of thepresent invention further includes a method of replenishing the sodiummetal employed in the sodium dispersion utilized in the desulfurizationand demetallization of the present invention. This is accomplished byreacting the precipitated sodium sulfide with hydrochloric acid so as toproduce a solution of sodium chloride which can be employed to providereplenished sodium metal through electrolysis.

The process of the present invention, including the cyclic naturethereof, can best be described by reference to the accompanyingdrawings.

As shown in the figure, a raw crude oil or similar virgin petroleumfraction enters through line 1 into a contactor 5 where it is combinedwith a dispersion of sodium metal entering the contactor 5 through line4.

The dispersion of sodium metal entering contactor 5 through line 4 isproduced by mixing a molten sodium such as produced from theelectrolysis of sodium chloride in a dispersion vessel 6, the moltensodium entering such vessel through line 2. The dispersion is producedby mixing the molten sodium with a normally liquid hydrocarbon enteringthe dispersion vessel 6 through line 3. Suitable hydrocarbons used forproducing the dispersion of sodium metal employed in accordance with thepresent invention include, for example, n-butane, isobutane, nhexane,n-heptane, n-octane, etc.

In the contactor 5, which need not be operated at elevated temperaturesand which preferably operates at ambient temperatures the sulfurcontaminants present in the cold crude oil or other virgin hydrocarbonfraction combine with the sodium metal of the sodium dispersion toproduce a precipitate of sodium sulfide. This reaction can be simplyrepresented as:

2Na+ Se Na S In addition, the metal contaminants present in the crudeoil or other virgin hydrocarbon fraction, e.g., primarily nickel,molybdenum, vanadium and cobalt will be displaced by the sodium metal ofthe dispersion, and will appear precipitated either as metallic sulfidesor the pure metal.

The desulfurized crude oil along with precipitated sodium sulfide andother procipitated metals or metallic sulfides leave the contactor 5through line 7, and enters a centrifuge or similar apparatus 9 whereinthe precipitated sodium sulfide and other precipitated metals, etc., areremoved by centrifugal force. The precipitate, con taining the sodiumsulfide contaminant and metal contaminants leaves the centrifuge 9through line 11 and subsequently charged to a repulper 13. In therepulper 13, a slurry is produced by contacting the precipitate fromcentrifuge 9 with a light hydrocarbon fraction, e.g., butane, hexane,heptane, etc., entering the repulper 13 through line 15. While not shownin the figure, such light hydrocarbon fraction can result from thefurther distillation and fractionation of the disulfurized crude oilproduced in accordance with the present invention, the light hydrocarbonfraction being only one fraction produced from the fractionaldistillation of the crude oil.

The slurry produced in repulper 13 exits through line 17 and enters afilter 19, preferably operated continuously. The filter employed can beany conventional filter press or similar apparatus generally employed toseparate liquid and solid portions from slurrys, dispersions and similarsystems. From filter 19 the filter liquor consisting of the desulfurizedpetroleum fraction containing some light hydrocarbon leaves through line21 and combines with the liquor leaving centrifuge 9 through line 10.The combined filter liquor from centrifuge 9 and filter 19 is now readyfor further crude oil distillation and fractionation in order to providethe desired petroleum products. Such petroleum products will now have asulfur content below acceptable maximum limits since the sulfurcontaminants present in the crude oil or other virgin hydrocarbonfraction have been removed pursuant to the reaction of the virginhydrocarbon fraction with the dispersion of sodium metal. The crude oildistillation or similar fractionation is not illustrated in the figure,and any conventional workup of the desulfurized crude oil can beutilized. Again, as indicated previously, such distillation andfractionation of the desulfurized crude oil or other virgin hydrocarbonfraction can provide the light hydrocarbon fractoin employed in repulper13 to wash the precipitate from centrifuge 9.

The washed sodium sulfide exits the filter 19 through line 23 from whichit enters a reaction vessel 25 wherein it is combined with hydrochloricacid entering reaction vessel 25 through line 27. The reaction of thewashed sodium sulfide precipitate with hydrochloric acid produceshydrogen sulfide which exits reactor 25 through line 29 and sodiumchloride leaving through line 35. The reaction which takes place inreactor 25 can be exemplified as follows:

The liquid product of reactor 25 exiting through line 35 and containingsodium chloride can be sent to any conventional sodium chloride andother metalic chloride reclaiming system. After providing the requiredsodium chloride through conventional reclamation, such sodium chloridecan be employed in an electrolytic cell to produce the sodium metalinitially utilized in the desulfurization of the crude oil or othervirgin hydrocarbon fraction. The electrolytic cell (not shown) cancomprise any conventional electrolytic cell which is uitlized to producesodium metal and chlorine by the electrolysis of sodium chloride. Inthis respect, suitable electrolytic cells include, for example, aconventional Downs or Chloro metal cell employing molten sodium chlorideas an electrolyte. The molten sodium which is produced from suchelectrolysis of molten sodium chloride can be used directly indispersion vessel 6 to produce the sodium dispersion vessel 6 to producethe sodium dispersion utilized in the desulfurization process. Hereagain, the light hydrocarbon fraction entering through line .3 intodispersion vessel 6 can be separately supplied or can be a portion ofthe light hydrocarbon fraction produced from the further distillationand fractionation of the desulfurized crude oil.

The hydrogen sulfide which leaves reactor 25 through line 29 can beutilized in any convenient manner. Thus, for example, it is possible toreact the hydrogen sulfide in a Claus reactor (not shown) with air so asto provide molten elemental sulfur as a byproduct of the integratedprocess of the present invention.

As seen from the above description of the process in conjunction withthe figure, the process of the present invention comprises an easy andefficient way of reducing the sulfur content of crude oils and othervirgin petroleum fractions below acceptable maximum limits whileproviding sodium chloride as a byproduct of the integrated process. Thissodium chloride produced as a primary byproduct of the desulfurizationreaction in accordance with the process of the present invention can beused as a source of the sodium metal employed as a sodium dispersion inthe desulfurization reaction. Thus, 'by employing the sodium chloride asthe electrolyte in a contentional electrolytic cell, it is possible toproduce sodium metal which when dispersed in a light hydrocarbonfraction can be suitably employed as the desulfurization medium.

While the amounts of the various components employed in thedesulfurization process are in no way critical to the sucessfuldesulfurization of the crude oil or other virgin hydrocarbon fraction,generally, the light hydrocarbon fraction dispersion of sodium metal isemployed in an amount so that the same corresponds to about 001% toabout 10% by weight of the crude oil contacted therewith. Of course, theamount of sodium dispersion necessary for the desulfurization of thecrude oil or other virgin hydrocarbon fraction will depend on the totalsulfur contaminants present in the crude oil and in the degree ofdesulfurization desired. The above amounts, however, are generally thosesuitable for providing a desulfurized crude oil or other virginhydrocarbon fraction within maximum specified limits of sulfur content.

Similarly, the dispersion of sodium metal in the light hydrocarbonfraction can vary considerably with respect to sulfur content; hereagain, the sulfur content of such varying depending on the amount ofsulfur contaminants present in the crude oil and in the degree ofdesulfuri zation desired. Also, however, the nature of the sodiumdispersion is dependent to a minor extent on the stability of the sodiummetal dispersed in the light hydrocarbon fraction. Generally, sodiummetal dispersions containing from about 10% to about 80% solid contentare utilized. Of course, lesser or greater amounts of the dispersedsodium metal can be employed where desired for particular purposes.

The present invention will now be described by reference to followingspecific example. It is to be understood, however, that such example ispresented for purposes of illustration only, and the present inventionis in no way to be deemed as limited thereto.

EXAMPLE In accordance with the present invention, a crude Pennsylvaniaoil which has not been previously refined for the elimination of anycontainants or the removal of any undesirable constituents is contactedfor a period of one minute at ambient temperatures with a dispersion ofsodium metal in butane, the sodium content of such dispersion beingapproximately 30% by weight. The dispersion of sodium metal and rawcrude oil are introduced continuously into a contractor with agitationso that the dispersion at all times corresponds to approximately byweight of the contents of the contractor. The contents of the contractorare continuously withdrawn and delivered to a centrifuge which providesa desulfurized liquor for further crude oil distillation andfractionation and a precipitate containing sodium sulfide in a minoramount of precipitated metals. The precipitate from the centrifuge isfed to a repulper wherein the precipitate is washed with a stream ofbutane in a sufficient amount to rid the precipitate from unwantedcontaminants and provide a slurry of sodium sulfide which issubsequently filtered and reacted with hydrochloric acid to providesodium chloride and hydrogen sulfide byproducts. After removal ofresidual light hydrocarbon from the sodium chloride byproduct, thesodium chloride is melted and used as the molten electrolyte in aChlorometal electrolytic cell employing a molten lead cathode. Theelectrolysis of the molten sodium chloride in the electrolytic cellprovides a stream of molten sodium as a primary product with gaseouschlorine being evolved. The molten sodium is then ready for reuse as adispersion for the desulfurization of further crude oil by admixing thesame with a further light hydrocarbon fraction. By such a process, thesulfur content of the crude oil is reduced from an initial content of1.2% by Weight to a content of less than 0.008% *by Weight. This is Wellbelow acceptable maximum limits.

As used throughout the instant specification, the term cold crude oil ismeant to embrace those virgin petroleum products which are not preheatedprior to the desurfurization reaction.

While the present invention has been described primarily with respect tothe drawings and the foregoing specific example, it is to be understoodthat the present invention is in no way to be deemed as limited theretobut must be construed as broadly as all or any equivalents thereof.

It is claimed:

1. A cyclic process for desulfurizing crude petroleum fractions andproviding sodium metal by electrolysis which comprises (a) contacting acold crude petroleum fraction with a dispersion of sodium metal in alight hydrocarbon fraction under ambient temperature conditions; (b)separating the product of step (a) into a desulfurized crude petroleumfraction and a sodium sulfide precipitate; (a) reacting said precipitatefrom step (a) with HCl to obtain hydrogen sulfide and by-product sodiumchloride; (d) employing said sodium chloride obtained in step (c) as anelectrolyte in an electrolytic cell for the production of molten sodiummetal; and (e) forming a dispersion of the sodium metal recovered instep (d) in a light hydrocarbon fraction for use in step (a).

2. The process of claim 1 wherein prior to step (c) said precipitate ofstep (b) is washed with a light hydrocarbon fraction.

3. The process of claim 2 wherein said dispersion of sodium metalcompirses a dispersion of about 10% to by weight based on said lighthydrocarbon fraction.

References Cited UNITED STATES PATENTS 1,938,670 12/1933 Sullivan et al.208230 1,801,412 4/1931 Carlisle 208208 2,058,131 10/1936 Carlisle208--208 2,078,468 4/1937 Stratford 208-2S8 2,772,211 11/1956 Hawkes etal 208-208 OTHER REFERENCES Thorpes Dictionary of Applied Chemistry, 4thed. (1950 vol. X, pp. 807 and 808.

DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant ExaminerUS. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,565,792 Dated February 23, 1971 Inventor s) Frank B HAS KETT It iscertified thaterror appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

Claim 1, line 35 of column 6, delete "(a)" and insert (c) Signed andScaled this Twenty-first D y f September 1 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Atlesring Officer (ummissiuncr uj'lalemsand Trademarks

